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For those of you who make S/L jumps, what exactly are you using for the line? What exactly is "brake cord"? How are you attaching it to the PC, and/or canopy, and how much line between the attachment and the tie off?

Okay, 200' object, freestanding, nice landing area. I've read how some experienced jumpers would freefall this object, handheld, and some would even go stowed. (I've seen the nice Xray photos in the Accidents category over on BLINC) What are the advantages of going SL, PCA, vs freefall, besides the obvious quicker canopy extraction.

thanks

Rod

(insert favorite pre-post disclaimer here)

I personally use 80lb break cord, tied to a piece of dacron suspension line, which in turn i usually lark's head to the object. I connect the bridle to the break cord with a rapide(sp?)link(canopy connector link)at the p/c end.
The break cord is what it sounds like: a cord designed to break at a pre-determined point. In this case, 80lbs. Most of the manufacturers sell it.

As far as the 200 footer goes: I'd s/l it.
But, then again, I'm a big wuss.

I'm the same as 704, I use 80lbs. break cord. I do rig a little differently thought. I use a peice of 13mm - 15mm climbing rope tied in a loop then looped around a hard point at the exit, tie my break cord thru the bridle, leaving the pilot chute on, and around the climbing rope with a surgeons knot.
I have done 200' both s/l and pca, with a proper pca from someone you trust, I prefer the pca. Don't know why just feels better.
Although you can freefall 200', I don't think that I would have the balls, but we have talked about it at the exit point, just none of us have ever tried it. I have freefallen 260' and that was scary enough.

Okay, I'm pretty sure I'm getting the right picture, but can anyone post a drawing of your favorite setup? Do both of you actually loop the break cord?

Same here.Thanks BASE 700

Yo!!

Hopefully 704 will post a pic, I know he's at home now doing nothing...with a new camera, and slick computer....but like he said, he's a wus so I'll do it tonight if he hasn't by then.
Faber, no problem at all, I used some yesterday off a 240' span, had a nice opening and a very fast, but soft landing. I'll try to send you a compressed vid of it later. Hope all is well for you.
Also, I'd rather do a S/L than a PCA, cause all my friends think its 'cool' to throw your PC past you right after the ya, in C-ya. They call it freefall assist
Later
Blair

As long as its under 10mb you can send it to my mail,or else try to use your msnAll is fine here

Why aint i suprised

Edit:by the way i manneged to save that poster,you should have seen my insurance guy as he payed me a visit(new insurance that cover BASE)

see if this helps...

the second pic is the s/l larksheaded to a barstool...

700...nice job with the IFR jump up north!
i'm really sorry that i couldn't make it...
let's get back to tearin' up the local scene, eh?
we could always start in your back yard!

DWAI!

Thanks 704 That's what I was having problems seeing, I understood the explanations, just couldn't get the picture, but it's clearer now.

One question though: Does it matter what type of barstool you use, I mean, probably don't want one too heavy, with the climb and all.

Rod

Ahhh...When faced with this dilemma one is dealing with the proverbial double edged sword...
Too heavy a bar stool, and the climb becomes brutal.
Too light a stool, and you run the risk of bringin' it back down with ya and a total.

'Tis definitely a very personal choice...

Thanks guys!!

In the picture, the break cord is looped...does this not increase the force required to break away... Looping the cord would give you twice the force required to break away since it is divided by two pieces of break cord.

It's still one piece of Break cord when using a loop. It will break in one spot therefore minimizing any added breaking force. It will not double the amount of force required to break it.

So the cord will most likely break at the point where it is looped through the peice of suspension line in this example, right? Therefore leaving the remaing cord that is larksheaded to the structure?

Would it be just the same to have the single loop attached at the structure and the larkshead on the supsension line so as not to leave trash behind?

Thanks
Rod

If the piece of the structure you attach to has a sharp edge, you may find the cord breaking prematurely (essentially being "cut" by the corner of the attachment piece).

I always use something else to tie to the structure. If it's a rounded bar, you should be able to get away with tying the cord to it, but if it's square, be careful of premature breakage.

I see what you are saying, but my physics studies tell me differenly. If the force was applied directly toward and away from the PC and the larks head, you would be pulling on two pieces of break cord. I know that practical experience is worth a lot more than theoretical calculation in these situations, I was just trying to calculate the whole thing out (nerd style!)

> So the cord will most likely break at the point where it is looped through the peice of suspension line in this example, right?
Not exactly. The break cord tends to break very close to the knot (=the weakest part of the whole "system", granted that you avoid sharp bends around sharp corners), that's why we do the surgeons knot onto the break cord: such a knot minimizes the "sharp bends" on the cord, letting the system to have a break load very very close to the break load of the "perfect" (=without knots) cord.

> Therefore leaving the remaing cord that is larksheaded to the structure?
Normally, you end up with leaving ALWAYS some piece of static line (=non-breaking rope) attached to the structure. Sometimes, the (broken) break cord remains into the loop of bridle, sometimes the (broken) break cord remains into the loop of the static line, that is fixed onto the structure of the object.

> Would it be just the same to have the single loop attached at the structure and the larkshead on the supsension line so as not to leave trash behind?
It is NOT such a huge pollution to leave behind few pieces of ropes behind.
Listen to what Tom said: it is NOT wise to tie the break cord directly onto the (metallic) structure. It is much better ALWAYS to tie the static line onto the structure, so having such a static line to "absorb" any unevennes of surface/structure, allowing the break cord to break exactly in the same way/situation/load on ALL your jumps.
Furthermore, using the system break cord+static line you have a double advantage:
1) you use a very small amount of break cord per jump (I use 10" - 25 cm of break cord on each of my SL jumps)
2) as static line, granted that you are going to lose it, you can use a cheap line/rope, provided that you do a double/triple/quadruple loop onto the structure; personally, I use a 1/6" - 4 mm rope (used in boating) and I do a triple loop onto the structure.
Plus, it is a very nice and "fast" set up: I prepare at home the break cord loop passing through the loop in the bridle (actually, I use a special bridle made up of a dyneema 5.5 mm - 1800 kg climbing rope, but this is another story), I pass through this break cord loop about 1 m of the above 1/6" - 4 mm rope, I leave it there and I pack all this nice stuff into the PC and I put this set up into the BOC as if it were "going stowed".
Then I climb onto the object, I approach the exit, I don the rig. At this stage, I pull all the stuff out of the BOC, and I usually do a triple loop with the 1/6" - 4 mm rope onto the structure, passing also ( ) through the (already prepared) loop of break cord. Since I do this stuff mostly at night (=very scarse visibility), it is much easier to handle and to make knots with the 1/6" - 4 mm rope than to handle and to make (surgeon) knots with the break cord.
Just my 0.02€.

> If the force was applied directly toward and away from the PC and the larks head, you would be pulling on two pieces of break cord.
You are absolutely right on, chap!!!
The "80 lb - 36 kg" rated break cord is rated so by BASE gear manufacturers because you are meant to use it closed in a loop (and then closing the two ends with a surgeon knot). Such a "system" breaks at 80 lb - 36 kg.
Now, it is quite obvious that when with the bridle you are pulling and you are approaching the 80 lb - 36 kg, actually you are exerting a force of 40 lb - 18 kg per each of the two "branches" of the break cord forming the loop: whichever of the two "branches" is slightly weaker than the other, it will break there.
The break cord we use is a 80 lb - 36 kg break cord granted we use it in a loop fashion (each of the two "branches" takes half on the load), but the break cord in itself is a 40 lb - 18 kg break cord.
If you consider the following set up: fasten a loop with a knot around the structure, then coming off this knot there is the break cord pure and simple (= a single line of break cord) for few (or many, it's the same!) inches/cm's, then fasten the other end with a loop and a knot around bridle loop: such a system is going to break at 40 lb - 18 kg, be sure about that!!!!!!!!
There must be a reason why, as static line, I use cheap (boating) 1/6" - 4 mm rope and I do a triple loop around the objetc structure: 1 loop = half load onto the rope itself, 3 loops = 1/6 of load along any of the 6 branches of rope.

I had an idea for a system that wouldn't leave anything behind at the anchor point.

I thought of the snag possibilities when the sling whips around, but as long as there aren't any huge burrs on the beam or rail, it should be okay.

The spectra is very strong so I'm confident the system will give exactly where it's supposed to.

Let me know if you see any problems with it.

P.S. If my highschool drafting teacher saw this he'd kick my ass.

You forgot your pilotchute dont SL whith out... or else i think its a super system,i think ill make one myself(if theres no other coments than the pc)..

Hello --

Not that this system wouldn't work, but one thought comes to mind at first glance. It seems to me that this system would require a greater force to actually break the 80lb break cord.

Looking at the picture, when force is applied to the system, the load will have to travel up through the climbing sling and over the railing and then onto the break cord itself. Essentially, you're introducing a pulley effect with this system, resulting in a higher force in order for the break cord to snap. As to how much force this is, I don't know. But it could be enough to lead to center-cell stripping, etc...

Thoughts?

Bryan

My logic is that since spectra slings don't stretch at all, the load will be transferred to the breakcord.

The pilot chute was left off the illustration for simplicity. I had hard enough time drawing a passable rapide, can you imagine if I'd tried to draw a pilot chute???

I wonder if we could recruit a physics wizard to explain exactly how this setup would transfer load to the breakcord.

Edit: After more thinking about this, it seems to me that the pulley effect is not an issue. If one end of the breakcord was anchored to the bridge after running aroung a handrail or beam, then I could see how the friction from the "pulley" point could be an issue. The way I set it up, the breakcord will start loading the instant weight is applied.

It seems to me that since both ends of the static line sling are attached to the same loadpoint, that both sides must share equal amounts of the force. Since the breakcord will part at 80 pounds, as soon as the system is loaded to that point, the breakcord will give. It's a weak link designed into the system.

Bps:
> …It seems to me that this system would require a greater force to actually break the 80lb break cord…
> …As to how much force this is, I don't know…
Simply, twice as much force than the “traditional” set up of break cord.

Rfarris:
> I guess my uneducated reasoning saw the thicker rope taking most of the load, and eventually transferring it to the smaller cord.
No. it is NOT a matter of how thick is any rope/cord. It is a matter of how many “branches” there are to bear the load. Quite simple. 1 branch (=1 single line of rope/cord/whatever): full load; 1 loop (=2 branches): ½ load; 2 loops: ¼ load on each branch and so on. Then, in case of 1 loop, each branch takes ½ load: the system breaks where the one of the 2 branches is weaker (=the one that has got lower break load) than the other.

Dexter:
> My logic is that since spectra slings don't stretch at all, the load will be transferred to the breakcord.
Yes, the spectra sling streches very little (no system/no rope has got infinite rigidity), but that is NOT the point. The point is, as I said before, that the full load (=the force transmitted by the bridle) is divided by as many times as the number of branches of the system.

> It seems to me that since both ends of the static line sling are attached to the same loadpoint, that both sides must share equal amounts of the force.
Yes, this is true.

> Since the breakcord will part at 80 pounds, as soon as the system is loaded to that point, the breakcord will give. It's a weak link designed into the system.

Not at all. Yes, the loop of break cord will part at 80 lb - 36 kg, but to get to 80 lb - 36 kg on the loop of break cord, you must pull the bridle with a 160 lb - 72 kg force.
Can you see the scenario? You have a pulling force on the bridle of 160 lb - 72 kg (you are about to break the system): this force is transmitted entirely on the rapid link. Then, the force of 160 lb - 72 kg is divided by two simply because there are two branches after the rapid link towards the fixed point onto the structure: two branches forming the sling loop. Each branch of the sling takes (=must take, forces can neither disappear nor increase, they can only be distributed/shared among various parts of a static system) half of the load: so each of the branches of sling takes 80 lb - 36 kg. Now, there is one branch of the sling that contains the loop of break cord: yes, it is going to part, but at this stage you are exerting, through your body, harness, lines, canopy, bridle a force of 160 lb - 72 kg, that is exactly the double of the force at which the system is supposed to be loaded and break.
Be careful: in a static system where there are forces that are exerted along a pillar/rope/line/whatever, any time along such a system is inserted a “loop”, each branch of the loop takes half the load (the total force transmitted can neither vanish nor increase).
Remember that with a suitable system of pulleys/ropes/turns of the rope along/around the pulleys, if you anchor such a system on a high point that takes all the load (=weight), exerting with your hands/arms a small force you can easily pull up a very heavy load: a grand piano, a safe, a car, whatever. The more load/weight you want to lift, the more pulleys and the more passes of rope through/around the pulleys need to be done.

Now, to take the good in your system, Dexter, you should simply use the break cord in the following way: you do one loop with a knot around the rapid link, then, off this loop/knot must come out only one single line of break cord (=the break cord pure and simple), then this single line of break cord “travels” all alone towards the loop in the sling: here you fix it with another loop/knot. This system is going to break when a force of 80 lb - 36 kg is exerted by the bridle onto the system.

Just after I wrote the above, I am wondering why you are use the rapid link, a component that is unnecessary (and that could fail…), at this stage. Has the sling got two (small) loops? You fix one end of sling with a larks head knot onto the bridle loop, then you fix the other end again onto the bridle loop using the break cord with a SINGLE LINE OF BREAK CORD (loop/knot, single line of break cord, loop/knot). Furthermore, the rapid link creates a sharp bend for the break cord: this way it could break at a load lower than the load it is supposed to break. We use static lines onto the structure to avoid sharp bends/sharp point of metallic structure to make the break cord properly, and then you introduce a very sharp bend through the rapid link (even if smooth surface, but still is very sharp bend (=small curvature radius))?!?!?!?
Just my 0.02€.

That was exactly the explanation I was looking for. Thank you for taking the time to write that.

I also spent a few hours researching various pulley systems and mechanical advantage and came to all the same conclusions. I stand corrected.

I am still going to do pull tests and see how much I can vary the breaking strengths. I do know that you can greatly vary the distributed load (and thereby changing the breaking point) by changing the angle of the sling.

As far as why I used the rapide, that's a good question. A girth hitch (larkshead) is a better choice. I guess it stems from my climbing background where nylon rubbing on nylon is bad. In this situation where friction is a minimal concern, the larkshead is the way to go.

Back to the drawing board....

Christ and I'm thinking about getting into BASE? I'm just not smart enough me thinks...

And what exactly makes you think we are?
-

> Christ and I'm thinking about getting into BASE? I'm just not smart enough me thinks...
Dude, do not think that all the things we know are only a "product" of ours. It took us a lot of studying through the Internet, studying from climbers, from friends that can give you an answer, from friends that have done it before, and once someone has figured it right and tried it on field, it becomes "the law" and we move on from there... ...still in time to revise the consolidated practice if in case!!! Otherwise, we do not invent any more and we do that particular trick all the time as before!!! What works well MUST NOT be changed!!!! And we pass it to our friends!!!
See the case of alpinism/climbing: all the techniques/tricks/equipment you need to know/use for 99% of climbs are already known and very well consolidated from pratice: we simply need to ask to the right people to pass you on the right information. No need to invent anything unless you want to do something really new/strange.
Internet has been the "great normalizer": once a practice/trick/habit/whatever is well proven that works, it can passed to ALL THE WORLD (=our worldwide community)!!!!!
That's what the forum in Internet are made for!!!

I THINK WE SHOULD ALL MAN UP AND FREEFALL THE FUCKING THING.
What a bunch of pussies we are.

> What a bunch of pussies we are
Yeah, I thought we are something about that.... ...nobody is perfect...

heh heh... okay... I'll watch you and if you do okay I'll be right behind you.

gardner

I agree that spectra is very strong and abrasion resistant material - however, I think gemini cord would be more appropriate for this use. Gemini cord is very thin, but very strong (kevlar and spectra combination), and is pretty stiff - which I think would allow for a more fluid torque around the point of attachment than the more floppy spectra sling. I think gemini cord also shows superior edge cut protection/resistance so you wouldn't have to worry so much about angle iron etc...

just my 02cents

sum1

they sell gemini cord here

You can buy gemini cord at any REI or climbing store.

I like the sewn spectra slings because there's no knots to snag on. The double or triple fisherman knot used to loop gemini cord (like when you thread larger hexes) can be a pretty good snag point if you don't pay close attention to where you place the knot. Also, gemini is pretty slippery and if you're unfamiliar with the proper knot to use, your loop can fail. A sewn and rated spectra sling doesn't have these problems.

I don't see how gemini cord would offer any advantage over a spectra sling.

Hey 689, I went back to the proverbial drawing board and this is what I came up with. It's super clean but would require a rigger to construct it. I like it, let me know what you think...

would looping JUST break cord and no sling be bad in someway I guess? The point of the sling is to do what? Distribute the weight evenly or some such? Sorry this may be a really dumb question

The breakcord is the weak link in the system and you want to protect it from the object itself.

You need the breakcord to part at 80 pounds to ensure a safe deployment. If you're on a low jump and the breakcord parts before the canopy is at line stretch (or even extracted........ chills...) you're done.

If you loop the breakcord over a handrail with a sharp edge or a piece of angle iron, your static line could break at a much lower tension.

ok, i knew i wasnt thinking that through at all

thanks

The thought I had - which I didn't really explain - is now absolved by your latest drawing, at least during the breaking of the break cord stage, by the lack of the pulley effect - in the older version, the stiffness of the gemini cord would help it to experience a lower coefficient of friction when coming around the object, at least less than a spectra sling. the spectra is so supple, that it likes to create sharper angles than something that cannot be bent upon itself as easily. It also has more small pile like fibers that will interact with small irregularities of the object causing higher friction coefficient as well.

gemini cord has edge cut resistance far superior to spectra - so that was one more thought on how it has less friction around the point. however, i agree about the knot being super snaggy... that would certainly suck to be left hanging there! Maybe the know could be minimized to a water knot and hid inside the bridle attachment point... but this would be only for the first drawing.

For the second drawing, it would be much more difficult to construct gemini cord... and I think this latest drawing looks like a much better system.

In the modified drawing, the friction factor doesn't need to be considered until after the break cord has broken - at which point you just have to worry about the bar tacks snagging the object attachment point - or, I guess, rig it in a loop to avoid the blocky bar tack.

Another option might be to use dacron or some sort of kelvar kite line that can be fingertrapped and sewn closed - much like toggle settings etc... - this might help create more snag-proof loops like you'll need for the latest design.

Good thoughts dexter,

Cheers!

> Hey 689, I went back to the proverbial drawing board and this is what I came up with. It's super clean but would require a rigger to construct it. I like it, let me know what you think...
It is a very good design indeed. I really like it. Provided there is ENOUGH slack for the "fixed" part of sling (to bridle) with respect to break cord loop, that in this case is going to break at 80 lb - 36 kg.
The other remark I would like to point out is that, once on the object/handrail/fixed point on structure/whatever, you must do a good thinking about the "free" end of spectra sling that, after break cord failure, is going to pass around "fixed point". This "free end" is going to pass around "fixed point" and clear itself with a whip stroke, so you must be absolutely sure that with such a whip stroke it DOES NOT touch any other part of structure, possibly hanging up/entangling anywhere (but this possibility exists with ANY design involving taking with you break cord/static line).
One very last remark: why use (exclusively) spectra sling? What about using 5.5 mm - 1800 kg dyneema climbing rope? Or similar rope? The loops, in this case, can be made with suitable knots, even if a rigger with proper sewings could do a cleaner job. Still being very careful about knots/thickenings (because of sewing) on the "static line" NOT hanging/entangling anywhere because of the whip stoke.
My compliments indeed, Dexter, I think your design, with possibly small modifications/personalizations, could be the set up to go!!!!

Dexter.. i think you should hurry up and get patent on that one im looking forward to see if you make some video that shows it in action

I have no idea how to go about getting a patent.

I think one of the manufacturers would probably be able to make some money off of it though. If they sold these I would have bought one a long time ago. Maybe they'll have some input.

you could ask Tom to delete your pics then sell them to the manufactors

well i dont have a copy ...yetbut i doubt you gonna delete it before i have downloaded the pic

Just wanted to say THANKS to all those who have posted and offered advice to my original post.

On a side note, how and where is 80lb BREAK cord advertised? Where do I find it? ParaGear? WalMart?


cya
Rod

vertigo sells break cord by the yard (I dont know what the specs are on it):

http://www.vertigobase.com/html/prod_pricelist.htm

This what you were thinking of? Dacron and 1000 lb Vectran.

Hook

That's awesome!

Wanna sell me one?

It's a fantastic set up, Hooknswoop!!!!!
Not to put your idea/work down, but the only downside of your sling is that, being made from dacron/spectra parachute line, yes, it is very robust but it is NOT abrasion resistant.
And, being so small and NOT abrasion resistant, I see that thing not working very well in a set up where the handrail/whatever is sharp/sharp edge/small metallic protrusion popping out of surface/whatever. In the long/medium term, the dacron/spectra sling is going to have a smaller section due to abrasion suffered with contact with metallic surfaces.
My small contribution: why don't you manufacture EXACTLY the same set up but using a, let's say, 4 mm dyneema climbing rope? It's got a 750 kg - 1653 lb Break Load, and, more important than that, its sheath is MADE FOR resisting to abrasion (being made for the alpine environment to be dragged around all over the rocks).
I already manufactured "your thing" using such a 4 mm dyneema rope, presently creating the 3 loops with knots (not jumped, ...yet...).
Yes, indeed, it is a much smarter idea to have the 3 loops sewn by a rigger using inserts and whatever, so having a much thinner appearance. I shall try to have it done more properly by a rigger. I shall let you know.

could you post a pic?

BUMP
Im WERRY interested in this Carry-on SL
How much has been tested? does any have the messurements i´ll need to make one.

pro´s and con´s please

Thanks

I would be careful of looping the break cord too loosely. If you don't snug the loop of break cord up tight, it will "snap" and shock load the break cord before the canopy reaches line stretch. This could potentially result in premature breakage.

Basically, make sure that no matter how you illustrate your knot on the internet, when you tie it, make it tight against itself, to guard against premature breakage.

Could you post a pic of whar you mean?
i guess i got it right,but not sure..

personaly i use a 2.breakcord as a back up,just abit longer so you dont get double force to break it.